I made a locking device to prevent the bolts coming out.
1/Purchase qty 4, 5mm bolts approx. 20mm long, Bolt heads should be same size as the hex in the socket headed engine mount bolts.
2/ Fabricate from alloy bar, 4 pieces to the internal diameter of the steel engine mount tube that the engine mount bolts are recessed into and approx. 1/8 in longer than the distance from the head of the bolt to the outside edge of the steel engine mount tube. Thread the centre of the alloy bar plugs with a 5mm tap. Screw the 5mm bolts into the plugs using Locktite.
Ensure the engine mount bolts are Locktited and torqued into the engine.
Install the alloy plug into the engine mount tube ensuring that the 5mm bolt head is engaged into the hex of the engine mount cap bolt.
Using a 1/16in drill, drill a hole through the steel enine mount tube and the alloy plug approx. 1/8in from the outer end of the steel engine mount tube. Install a 1/16 S.S cotter pin through the hole and fold over the tails.
This should prevent the problems of the engine mount bolts coming out.

Jim,
What a terrific, creative solution to ensure a redundancy factor to this concern for all 12 builders/owners! You put your aircraft engineer experience to work! I'm impressed and very grateful! Possible to get some pics either via this thread or by email? Thank you so very much!

I purchased a set of inexpensive metric 3/8" drive hex sockets from Harbor Freight. The set had the correct size for the engine mounting hardware ... which, if memory serves me correctly, was 6 mm (but don't hold me to that).https://www.harborfreight.com/6-pc-3...set-69546.html

I also purchased the extended ball tip version when they were on sale for around $9.

The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.